Pretty good motors who can handle way more power than they are rated for (successfully tested at 10 times their rated power)

Hub motors will save you a fair amount of space for more battery and they are not actually that much heavier than a regular wheel+chain+sprocket system. Main drawback is that you have no way to change the gear ratio.

That's indeed a drawback. But once you find the correct gear ratio on an inboard motor you rarely change it anyways.
On the other hand you'll have a lot more space for a lot more battery, so this is to be considered too.

You can effectively change it by changing the voltage of the system. If you need higher speeds, increase the system voltage (and potentially the current). Depending on the motor wind, it can shift the power band around.

You can effectively change it by changing the voltage of the system. If you need higher speeds, increase the system voltage (and potentially the current). Depending on the motor wind, it can shift the power band around.

That is not gear ratio change, all that is doing is increasing the voltage.

It will accomplish exactly the same thing: increase torque while diminishing speed or increase speed while diminishing torque.
So it's not a ratio change if you want to get into the semantics, but in the end IRL it's just about the same.
Anyway, in practice it's hard to do because you'd had to rebuild your battery or change its configuration if it's modular. Just totally impractical.

Actually, now that I think about it and since you seem ready to consider gigantic motor options like a Phi27, you could totally buy a hub motor and convert it into an inboard motor. The only thing needed is a bit of lathe work to get rid of the rim (it can even be done by hand but a lathe is better, probably even possible to DIY a lathe using the motor itself as a power source). The big QS motors seem to be smaller in diameter than the Phi27, you can attach a sprocket instead of the brake disk (so you could do gear changes if you want) and essentially do the same thing. The advantages being that it would be much cheaper and a bit more compact. Just a thought.

I think you should mention your budget, as well as what you actually plan for your build. There are a lot of options when it comes to motors, but it will depend a lot wether you're ready to spend 500 bucks or 10 000.

Trying to get my hands on a QS 273 50H V3 - Rated for 8kw continuous, 23kw for up to 30 seconds, and they say that those figures are conservative. There are much larger versions that can do 14kw continuous.

This was my calculation sheet for the different winding options:

Options.jpg (60.78 KiB) Viewed 298 times

You can adjust the voltages of your own battery (assuming you haven't built it already), to get the ideal top speed trading off for torque.

I understand you want to get a variable gearing ratio during ride (so no changing tyres or voltages on the road), but if I can get a bike that has a top speed of 150km/h and has so much torque I can flip the bike on take off, where's the advantage? A marginally faster 110-150km/h?

If that is really important to you, because you want a great 1/4 mile time, then something with a 2 or 3 speed gearbox makes sense. But electric motors aren't like petrol motors. The maximum torque range is basically from stalled (0 rpm) all the way to about 80ish percent of max speed. The gains from a gearbox are very marginal. Why do you think Teslas (and in fact most electric cars) don't have one?

They are awesome controllers, very robust, and include a feature you might like called automatic FOC. You read about people talking about field weakening, well one method to do that is called FOC (Field Oriented Control). The Mobipus can enable field weakening automatically when you hit a certain speed. So say the controller can only normally go up to 88V, and that gives you 130kph. You can set the controller so that when it detects the 128kph (based on motor RPM), than field weakening will be enabled and you can go up to 160kph.

Field weakening lowers efficiency quite a bit, which is why this automatic feature is handy. Obviously, it would be better to simply get a motor that can do 160kph with the battery pack voltage you have decided to use.

The QS273 80H V3, with its default winding for a Kv of 14.5 (rpm/V) can do 160kph, with a 24in outer diameter wheel, if you supply it 96V. That's under ideal unloaded conditions. I would ask them for a custom wind, with a higher Kv, some of their other motors have a Kv of 16.2 (88V for 160kph), 17.7 (79V for 160kph), and 19.99 (70V for 160kph).

Also, just to note, you can't run PMSMs in series or parallel, they each need their own controller.